MATSE 259 Exam 4 QUESTIONS AND ANSWERS | GRADED A

MATSE 259 Exam 4 QUESTIONS AND ANSWERS | GRADED A austenite to pearlite (ferrite + cementite) Correct Answer: γ → α +Fe₃C isothermal Correct Answer: TTT curve is an ____________ transformation coarse pearlite Correct Answer: occurs at temperatures just below eutectoid (727°C), consists of thick layers, and has higher diffusion rates and slower cooling rates fine pearlite Correct Answer: occurs at temperatures around 540°C, consists of thin layers, and has lower diffusion rates and moderately rapid cooling rates longer Correct Answer: coarse pearlite has _______ lamellae shorter Correct Answer: fine pearlite has _______ lamellae proeutectoid Correct Answer: above and below the eutectoid temperature, a _____________ phase occurs bainite, spheroidite, and martensite Correct Answer: other micro-constituents besides pearlite bainite Correct Answer: this micro-constituent forms at temperatures below pearlite spheroidite Correct Answer: forms when a pearlitic or bainitic microstructure is held at temperatures below eutectoid for 18 to 24 hours carbon diffusion Correct Answer: _________ ___________ occurs with spheroidite, but no change in composition occurs martensite Correct Answer: micro-constituent that forms when austenite is rapidly cooled (quenched) at relatively low temperatures diffusionless; thermal Correct Answer: martensite formation is a _____________ and __________ transformation BCT (body-centered tetragonal) Correct Answer: structure of martensite critical quenching rate Correct Answer: minimum cooling rate required to produce a completely martensitic microstructure pearlite + proeutectoid phase Correct Answer: with slow cooling, austenite forms... bainite Correct Answer: with moderate cooling, austenite forms... martensite Correct Answer: with rapid cooling (quenching), austenite forms... tempered martensite Correct Answer: when martensite is reheated, it forms... hard and brittle Correct Answer: quenched condition of martensite is... below Correct Answer: heat treatment for tempered martensite is ______ eutectoid temperature ductility; toughness Correct Answer: relieving internal stresses in tempered martensite via heat treatment increases __________ and _____________ 250 to 650°C Correct Answer: temperature range for tempered martensite fine Correct Answer: with larger carbon content, _______ pearlite has a higher Brinell hardness number coarse Correct Answer: with larger carbon content, _______ pearlite has larger ductility harder; stronger Correct Answer: bainite is __________ and __________ than pearlite martensite Correct Answer: ________________ is the hardest, strongest, and most brittle steel microstructure annealing, stress relief, normalizing, austenitizing, and spheroidizing Correct Answer: different types of heat treatments annealing Correct Answer: a generic term used to denote heat treatment in which the microstructure and, consequently, the properties of a material are altered; previously cold-worked material is softened by recrystallization annealing Correct Answer: heat treatment where material is exposed to an elevated temperature for extended period of time then slowly cooled softness; specific Correct Answer: annealing relieves stress, increases ________________, ductility, and toughness, and can produce a ____________ microstructure heat to desired temperature, hold (soak) at this temperature, cool to room temperature Correct Answer: steps of annealing process annealing Correct Answer: negate the effects of cold work and softened and increases the ductility of a strain-hardened metal (recovery and recrystallization) stress relief Correct Answer: heat treatment to remove residual stress plastic deformation (i.e. machining), non-uniform cooling after processing at an elevated temperature (i.e. welding and casting), and phase transformations induced on cooling (i.e. martensite) Correct Answer: internal stresses can develop with... stress relief annealing heat treatment Correct Answer: component heated to recommended low temperature, held at this uniform temperature, and cooled to room temperature in air normalizing Correct Answer: refines grains and produces a more uniform and desirable size distribution (at least 55°C above upper critical temperature), transformed to austenite, then cooled in air full annealing Correct Answer: heat treatment in low to medium carbon steels to produce coarse pearlite in components that will be machined or experience extensive plastic deformation spheroidizing Correct Answer: carried out a temperature just below the eutectoid in which the spheroidite microstructure is produced cementite Correct Answer: coalescence of _______________ to form spheroid particles 15-25 Correct Answer: if the starting microstructure is pearlitic, spheroidizing takes ________ hours slowest; fine; cold work Correct Answer: rate of spheroidite formation is _____________ for pearlite, more rapid with _________ pearlite, and prior ______ ______ increases the reaction rate austenitized; quenching Correct Answer: heat treatment in martensitic steels is the continuous rapid cooling of an _________________ specimen in a ______________ medium (oil, water, or air) ferrous alloy Correct Answer: a metal alloy for which iron is the prime constituent composition of the alloy, type and nature of the quenching medium, and shape and size of the specimen Correct Answer: factors affecting the ability to produce a martensitic microstructure throughout the cross section of a component surface area; mass Correct Answer: rate of quenching can depend on the ratio of ____________ _______ to _______ of the specimen (rate of cooling) hardenability Correct Answer: a measure of depth to which a specific ferrous alloy may be hardened by the formation of martensite upon quenching from a temperature above the upper critical temperature surface; interior Correct Answer: high hardenability indicates that the alloy hardens or forms martensite at the ___________ and throughout the entire ____________ martensite, bainite, pearlite, ferrite Correct Answer: rate P, F, M, and B in terms of hardness austenite Correct Answer: M, B, P, a